A typical application of the present invention is in the removal of bolts from mining equipment, such as mills that utilise sacrificial segmented liners bolted to the internal casing of the mills which are regularly replaced during routine maintenance. Typically such mills may range in size from three meter to eleven meter in diameter and are lined with replaceable heavy steel segments attached internally to the mill casing by through bolting. In such applications the bolts become corroded and clearances between bolts and holes become compacted with ore fines. This results in difficult bolt removal at liner removal time. As a result the many bolts that are utilised to attach the liners to the mill shell: are often required to be freed manually by the use of large sledge-hammers. This is a difficult and time-consuming task that may result in injury to the workers.
While it is well known to use percussive devices such as jack-hammers and hydraulically powered hammers to provide repetitive impacts for many applications, they are not able to be manually guided into alignment with wall mounted bolts and other components. The applications of jack hammers are limited as the hammering effect produced by an electrically or pneumatically operated jack hammer does not provide the impact as would be provided by a sledge hammer, for example.
In known hammering devices capable of delivering such impacts, a high reaction force is produced which necessitates that such devices be carried by articulating machines or be rigidly attached to some support structure. This reduces their versatility and makes them unsuitable for many applications. Furthermore, it is difficult to quickly and accurately align such devices with the shank of a bolt or the like for effecting ready removal thereof.
International publication WO97/26116 by the present applicant describes a hydraulic linerbolt removal tool. The hydraulic tool essentially comprises a housing having a moil mounted at the forward end and a hydraulic piston assembly reciprocally moveable along the hammer axis between a striking position at which the piston assembly strikes the impact delivery member and a retracted position remote from the impact delivery member. A firing means is provided for hydraulically firing the piston assembly from its retracted position to its striking position under the control of actuating means. A reactive body assembly is moveable in the direction of the hammer axis by driving means towards the impact delivery member prior to operation of the firing means whereby the reactive body assembly may be energised by movement and subsequently decelerated to substantially absorb the reaction generated by firing the piston assembly. Recoil is thus reduced whereby the apparatus may be operated by hand with the apparatus being suspended about its centre of gravity at the work site.
This hydraulic apparatus requires a 2400 psi hydraulic supply. The apparatus also requires electronic control for timing purposes. The present applicant has determined that there is a need for linerbolt removing tools that are operable from a conventional compressed air supply.